1. Field of the Invention
This invention relates generally to a data processing method and apparatus in which figure data for drawing plural unit figures are generated from a sole figure data for improving the processing speed of the apparatus. More particularly, the invention relates to a data processing method and apparatus which may be employed with advantage in a graphics computer such as video equipment employing a computer, a special effect device (effector) or a video game machine, whereby enhanced data processing is achieved.
2. Description of the Related Art
It is common practice in the prior art to employ a video game machine wherein a main central processing unit (CPU) encloses a geometry transfer engine (GTE) which is a calculation processor for executing geometry processing such as coordinate transformation, perspective transformation, clipping or light source calculations. The main CPU defines a three-dimensional model as a combination of basic unit figures, such as triangles or quadrangles (three-dimensional model) for generating data for delineating a three-dimensional image.
When displaying, for example, a three-dimensional object, the main CPU resolves the object into plural unit figures and causes a GTE to perform geometry processing to generate figure data for drawing each unit figure. The main CPU is connected to a main bus and causes the figure data generated by the GTE to be transferred over the main bus 101 to a graphic processing unit (GPU).
On reception of the figure data from the main CPU, the GPU performs rendering processing of writing pixel-based picture data in a graphic memory from Z-values specifying the color data and the length of apex points of unit figures contained in the figure data (the information on the distance from the beginning point along the length), taking into account the color and the Z-values of all pixels making up the unit figure. The unit figure is drawn in this manner in the graphic memory. In addition, the CPU performs control for reading out the picture data written in the graphics memory to supply the picture data thus read out as video signals via a display controller, such as a CRT controller (CRTC) as video signal, for display on a display device, such as a television receiver, a cathode ray tube (CRT), liquid crystal or the like monitor. This permits the background of a video game, characters or the like to be displayed.
Meanwhile, the data of the unit figures, geometry-processed by the GTE under control by the CPU, are coordinates in the three-dimensional space of the apex points of the unit figure. Therefore, the data volume is irrelevant to the size of the unit figure. On the other hand, the drawing rate with which the unit figure is drawn on the pixel basis in the graphic memory is dependent on the size of the unit figure, that is the number of pixels making up the unit figure. Hence, if there are a large number of pixels making up the unit figure, drawing the unit figure is time-consuming, whereas, if the unit figure is made up of a smaller number of pixels, drawing the unit figure is not time-consuming.
Therefore, in continuously processing plural small-sized unit figures, it is a frequent occurrence that the figure data is not transferred in time from the main CPU over the main bus, despite the fact that the GPU has completed the rendering processing and is ready for performing the next processing. In other words, when a large number of small-sized unit figures are transferred from the main CPU to the GPU over the main bus, the transfer rate is limited by the main bus, with the result that it becomes difficult to improve the overall processing speed of the device.
Accordingly, there has been along existing need for enhanced data processing at increased processing speed. The present invention clearly fulfills these needs.